Potassium iodide composition of matter for photographic processes



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ROBERT JOHN, OF NEW YORK, N. Y., ASSIGNOR TO DAYL IGH'I' FILMCORPORATION,

CORPORATION OF NEW YORK.

v POTASSIUM IODIDE COMIlPOS ITION OF MATTERFOR PHOTOG-BAPHIC PROOESSF5.

Ho Drawing. i

To all whom/it may concern:

Be it'known that I, ROBERT JOHN, a citizen of the United States,residing at New York, in the county of New York and State of New York,haveinvented a certain new and useful Potassium Iodide Composition ofMatter for Photographic Processes, of which the following is aspecification.

My invention relates to a potassium iodide composition of matter forphotographic processes and has for its object the production ofa-photographic record of lights and shades in which the gradationbetween the recorded light-s and shades may be controlled.

A further object of my invention is to produce a series of picturestaken under different lighting and other conditions in which theevenness of gradation in each picture shall be approximately the same.If desired, hard pictures can be made soft and soft pictures can be madehard.

A further object of my invention is to obtain, in one embodimentthereof, a printing surface which is mounted on a suitable carrier andwhich represents photographic lights and shades in such a manner thatcopies may be made therefrom by a dye or inktransfer contact process.

For the purposes of illustration, my invention will be described inconnection with the formation of aprinting surface obtained by exposingto the action of light modified by the lights" and shades of a completednegative which it is desired to reproduce a sensitized emulsion mountedon a transparent carrier through which it preferably is exposed, whichthen is treated to form a hardened printingv surface.

Itis considered desirable in producing a printing surface to expose thesensitized emulsion through its transparent carrier rather than onitsoutside surface in order that the printing surface may be as close aspossible to the carrier. exposed on its outside surface, it is necessaryto strip the emulsion from its carrier in order' to remove theunhardened portions which will lie adjacent the carrier. Stripping theemulsion is a delicate operation which can be performed only by thoseskilled in the art and is likely to lnjure the image.

When an emulsion is exposed throughits transparent carrier, however,certain. dlfi.

If the emulsion is Application tied October 2, 1919. Serial no. 327,891.4

portionsadjacent the transparent carrier.

This usually is accomplished by the use of an excess of alkali, such,for example, as sodium carbonate, which opens the pores of the emulsionand carries the solution through.

The objection to this is that the excess of alkali has a tendency toaffect the image unfavorably, destroy the delicate intermediate shades,and make it too contrasting. In the second -place, an ordinarysensitized emulsion usually is in excess of one-thousandth of an inch inthickness, while the preferable printing surface adjacent the carriershould be very thin. substantially one ten-thousandth of an inch orless. As this ordinary thick emulsion will be penetrated deepl by thelight to which it is exposed, particu arly that portion of the lightcoming through clear spaces or light shadows in the negative which isbeing reproduced, the resultant printing surface after treatment willgive a relatively too thick printing surface in those portions. Thisundesirable thickness is in creased by the use of an alkali as referredto above. It is very difiicult, therefore, to t the darker ,portions ofthe negative recorfe d properly without having the lighter portions ofthe negative registered too heavy and deep.

One manner of overcoming the above difiiculties has been toincorporate'in the emulsion a light-restraining agent such as tartrazineor a chrome yellow pigment which hasthe property of absorbing or slowindown the action of the printing rays su ciently' to enable the darkportions of the negative which is being reproduced to be registered onthe sensitized particles in the emulsion adjacent the carrier. beforethe printing rays coming through light portions of the negative havepenetrated the emulsion so deeply as to form a printing surface which istoo thick in the portions corresponding to said light portions of thenegative. after the printing surface has been treated and the portionsof emulsionunaffected by light removal. The use of theselight-restraining agents, however, has disadvantages, among which may bementioned their detrring efiect on the sex st '10 I have discovered thatexcellent resiilts may tized emulsion so that a longer time of exposureis required. Although this additional time of exposure is not a serioushandicap in plate photography, it is important in motion picturephotography where the speed of running the'large number of individualpictures upon a motion terial factor.

picture fihn through the printer is a ma- In order to overcome thesedisadvantages,

. be-obtained by the use of a developer solution containin potassiumiodide which within certain limits seems to have the property of holdingthe lighter tones and at the the characteristics desirable for a contacttransfer printing surface. A softness of result also is obtained withoutthe too contrasting eifects which are undesirable.

A sample formulafor a developing solu tion containing potassium iodideis as follows: v

ayrogallic acid 1O grs.

ater to 1oz.

, Y ,B. I I. j Sodium carbonate 7O grs. Potassium iodide.. 50grs. Waterto.. 5ozs. ,Use one part of A to 5 arts of B. Within certain limitssodium su phite may be used with I tassium iodide, the exact amounts ofwhlch will be determined by the articular work in hand. A sample formu afor a developing solution containing potassium iodide and sodium,sulphite is as follows:

Water; 8.5 oz. 1lciyro llic acid 11 grs. eto 9 grs. Potasium bromide -1,4 grs. Sodium carbonate 200 grs. .Sodium sulphite 40to60grs. Potassiumiodide f 20 to 90'grs. Metol is' monomethylparamidophenolsul- P a -0 Hiscustomary in photographic work and particularly in motion picture workto control the evenness of fimshed prints by varying the amount of lightexposurein' different stages of the photographic process. This is yparticularly desirable in motion picture .work in order to give an evenlighting efl'ect to the .completed film where the parts have been takenunder va ing lightm condi tions. In addition to is evenness gf lightingeflect, I have found it possible to control the evenness of the pictureswith relation to the difierence between light and dark portions, so thatsome pictures will not be more contrasting than other pictures butgreater degrees of produced havi that all will have substantially thesame de-.

gree of softness or evenness of gradation.

A thousand foot reel of ordinary motion pictures, for example,ordinarily consists of many different scenes taken under var ing lightconditions. In making prints om the negative of such a picture, theuneven' ness in lighting can be.reducedby varying between light and darkportions, so that the.

completed motion picture will have a uniformity of appearance mostpleasin to the eye. Toaccomplish this result I rst develop thoseportions of a picture in whichv .the degree of gradation between'lightsand shades is at a minimum in a developer solution containing aminimum-amount of potassium iodide. When this portion of the film hasbeen developed, more otassium iodide is added and a ortion of t e filmdeveloped in which the egree of gradation between lights and shades iseater than in the first ortion developed. 1s added as portions of thefilm having adation are reached until the entire film 1s finished. Thiswill result in a completed film in which not only is there evenness oflighting but evenness of gradation between the light and dark portionsof the film. In making still pictures ore potassium iodide posedemulsion without destroying the light shades so that a less contrastinor more soft picture is obtained, particular y in the pro uction of aprintlng surface suitable for a dye or ink contact transfer process. If,on the other hand, an amount of sodium sulphite sufiicient to reduceheavy shades I was used, it .would destroy the light shades.

It is this 'p-roperty'of potassium iodide of re ducing the heavy shadeswithout destroying the light shades which makes it possib e to obtainauniform product as well as a desirable surface for contact transferprinting.

Many modifications of my invention will be'apparent to those skilled inthe art without departing therefrom or from the scope of the invention,my invention not being limited to the embodiments thereof chosen forpurposes of illustration but consisting of a potassium iodidecompositionof matter,

whereby the im-ageis retained. close to the earner and any series ofpictures may be the same egree of gradation between .lig t and darkportions thereof.

What I claim is: 1. A developing and hardening composi tioncontaining ahardening substance. and" an agent adapted partially to neutralize saidmamas hardening substance comprising potassium iodid, in such aneffective amount as to permit only a selective area of hardening.

2. A developing and hardening composition containing pyrogallic acid,and potassium iodid in such an effective amount as to permit only aselective area of hardening.

3. A developing and hardening composition containing pyrogallic acid asa hardening substance and a mixture adapted partially to neutralize saidhardening substance comprising potassium iodid and sodium carbonate, thelatter being present in sufiicient quantity with respect to the iodid,to prevent complete neutralization of the hardening effect of thepyrogallic acid so as to permit only a selective area of hardening.

4. A developing and hardening composition comprising an iodid saltpresent in insufficient quantity to completely neutralize the hardeningeffect of the composition, whereby only a selective area of hardeningwill result.

5. A- developing and hardening composition for photographic processescomprising the following:

Pyrogallic acid 10 grs. Sodium carbonate; 1,350 grs. Potassium iodid 250grs.

ater 26 ozs.

6. A developing and hardening composition for photographic (processescomprising Water, pyrogallic aci metol, potassium bromide, SOdlllHlcarbonate, and potassium iodid.

7. A developing and hardening composition for photographic processescomprising water, p-yroga-llic acid, metol, potassium bromide, sodiumcarbonate, potassium iodid, and sodium sulphite.

In testimony that I claim the foregoing, I have hereunto set my handthis 30th day of September, 1919.

ROBERT JOHN.

